Is there a trick to make Mathematica solve with one boundary condition?
?^2u=0
BC : u(x,0)=0, u(x,a)=0, u(0,y)=0, y(b,y)=100ºC
Show me distribution chart to assume 0< a <100cm, 0< b <100cm in steady state.
You may check this demonstration example: http://demonstrations.wolfram.com/SolutionOfTheLaplaceEquationUsingCoordinatesFittedToTheBound/